1. Field of the Invention
This invention relates to an integrated circuit package and, more particularly, to a moisture getter material provided within the sealed package which is capable of withstanding the high sealing temperatures required in package formation without degradation of the getter properties of the material.
2. Description of the Prior Art
The problem of moisture in hermetically sealed integrated circuit packages has not been uniformly recognized in the prior art and, in any event, has not been adequately handled.
In the formation of an hermetically sealed semiconductor device or chip package, it is necessary to exclude moisture from the sealed cavity. This is because the device is mounted in such a manner that, after reaching a high temperature, turning off and cooling, the substrate which carries the device cools down first. The substrate is designed to carry the heat away most efficiently. The result is that the surrounding medium and the device will have a temperature differential, the device being the colder. Any moisture present in the cavity will therefore condense on the surface of the device and leads thereto, such moisture being then available as a liquid electrolyte to transport ions and promote corrosion. Therefore, it is desirable to eliminate the moisture from the package. The origin of the moisture is multifold. First, the atmosphere in the sealing furnace has some; second, some of the glasses themselves as a result of fusion liberate water; and third, the ceramic material which has some porosity has moisture in it which goes into the micro-cracks therein and by osmotic pressure is extremely difficult to remove.
One problem in the use of standard getters to remove moisture is that they do not adequately retain their getter properties after being heated to the temperatures required to hermetically seal the package.